fix: cast $match[1] to float in WP_DuotoneGutenberg::colord_parse_hsla_string()

[justlevine]

What?

This PR fixes an issue in WP_Duotone_Gutenberg::colord_parse_hsla_string() where the string results of preg_match() are passed to ::colord_parse_hue() which expects a float for its first parameter.

Why?

While this issue was surfaced by PHPStan (via #66693) it can be remediated independently as part of #66598

How?

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

Before	After

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Co-authored-by: justlevine <[email protected]>

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